[Black_GT]

Hi, a few weeks ago I stupidly reversed into my (low) garage with the roof aerial up, and only noticed as it started bending.... Fortunately it didn't physically break the aerial, and it looks fine and can still be pushed in and extended. However, it no longer works - radio reception is exactly the same with the aerial pushed in or extended!

I thought the most obvious explanation was that bending it had snapped something internally, either breaking a circuit or causing a short. Checking between the aerial and its connector with a DC multimeter shows continuity between the inner pin and aerial, and between the outer coax and roof earth point - and not between other combinations, which seems correct.

Does anyone have an idea what the problem is, and how I can fix it without just replacing the aerial?

[g259fsg]

From the measurements you've done, that is very puzzling. I assume you are getting low resistance (less than a few ohms) when checking continuity. Does the connection between the aerial and the coax inner change at all when you push the aerial in and out? I take it the radio reception is now quite poor? Is it better when you put a bit of wire in the radio aerial socket.

I had the same kind of aerial damage years ago with our 214. It still seemed to work, and I just put a piece of thick galvanised wire inside the aerial and pushed into the broken end on the car. I did eventually replace the aerial with a complete new assembly I got from Rimmers. I now keep it mostly tucked in so it doesn't catch on things. If you are going to swap the aerial, tie a piece of string on the end of the old cable before you pull it out so that you have a draw line to pull in the new cable down the door pillar.

[Black_GT]

Yes, very low resistance. Unfortunately I have already the aerial once and a year ago (the string snapped, it was an absolute nightmare!).

The reception is bad yes - I tried temporarily reconnecting the original aerial, which is snapped at the base, with a wire stuck out the end and it was way better.

[g259fsg]

Definitely seems like there isn't much RF signal getting through even though the DC measurements look OK. It's like there is a capacitive shunt across the cable that is killing the high frequencies but doesn't show up on the DC resistance measurement across the cable. Another option is to unscrew the aerial fitting at the roof and see if there is any obvious damage. You could also open up the coax cable and see if the fault is in the aerial assembly or the cable, most likely the assembly. BTW, have you checked all channels are affected equally, assume you are using FM broadcasts. Cable faults can sometimes cause reflections so some frequencies are more affected than others.

[Black_GT]

That would make sense - I've unscrewed it and had a look, the plastic tube that the aerial retracts into is cracked, all the solder joints look good though.

I've checked on FM and DAB - interestingly, while reception is almost zero on FM it's mostly passable on DAB, even with the aerial fully down!

If I do decide to replace the receiver, I'm tempted to cut the coax cable in the car and the coax cable on the new aerial, and attach the cut ends using screw coax connectors - is there a reason why I shouldn't?

[g259fsg]

I think it would depend how much space you've got to tuck it back in after you've made the joint. If you go that way, it might be better to solder the ends together and insulate with some heat shrink, so that the joint isn't much fatter than the cable. Should be able to get it back into the door pillar then. Before connecting up the new aerial, you could check the cable is OK by attaching a piece of wire on the cable inner to simulate the extended aerial.

[Black_GT]

Thanks, yes that sounds like a good idea!